Cardiac stress tests

Porya Hassan Abadi

Introduction• Diagnostic test for coronary artery disease• Main aim is to assess the coronary flow

system• Measures ability of heart to respond to

stress• Stress is induced by drugs or exercise

under clinical supervision

Clinical case• 50 y/o female with diabetes, HTN, smoker• Nonspecific substernal chest pain• Slight dyspnoea • ECG nonspecific• Normal cardiac markers

Indications• Diagnosis of coronary disease in patients

with:– Stable chest pain– Unstable chest pain stabilised with

therapy– Previous MI– Post revascularisation (CABG)

Contra-indications• Acute myocardial infarction (within 2 d)• Unstable angina not previously stabilized by

medical therapy• Uncontrolled cardiac arrhythmias causing

symptoms or hemodynamic compromise• Symptomatic severe aortic stenosis• Uncontrolled symptomatic heart failure• Acute pulmonary embolus or pulmonary infarction

• Acute myocarditis or pericarditis• Acute aortic dissection

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TYPES OF STRESS TESTING• EXERCISE

a. Treadmillb. Bicycle

• PHARMACOLOGICALa. Adenosineb. Dipyridamolec. Dobutamined. Isoproterenol

Physical stimulation• Test is done by exercise on treadmill or

pedaling an stationary bicycle.• Constantly monitored (ECG,BP and heart

rate)

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TEST OF CHOICE IN THOSE WITH:• NORMAL BASLINE ECG • ABLE TO EXERCISE• NO PRIOR REVASCULARISATION

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How long? How fast?• Maximal Test: The patient achieves 85% of

MPHR (maximal predicted HR = 220 - Age)

• Submaximal Test: The patient becomes symptomaticchest pain, dyspnea (MPHR generally not achieved)

When the termination is needed?• Drop in systolic blood pressure (SBP)

despite an increase in workload• Moderate-to-severe angina • Increasing neurological symptoms (eg,

ataxia, dizziness, near-syncope) • Signs of poor perfusion (cyanosis or pallor) • Subject’s desire to stop • Sustained ventricular tachycardia • ST elevation (> 1 mm) in leads (other than

V 1 or aVR)

Safety and risk of exercise test

• Nonselected patient population: Mortality < 0.01%

• Within 4 weeks of MI: Mortality = 0.03% and Morbidity = 0.09% (reinfarction, cardiac arrest)

Pharmacological Stress Test • Stress is induced using agents such as :

1. Vasodilators such as: Adenosine and Dipyridamole not used asthma or COPD

2. B2 agonist such as: Dobutamine

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INDICATIONS OF PHARMACOLOGICAL STRESS

TESTING• Patients inability to exercise adequately

because of physical or psychological limitations.

• The chosen test cannot be performed readily with exercise (e.g. PET scanning).

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METHODS OF DETECTING ISCHEMIA DURING STRESS

TESTING• Electrocardiography• Echocardiography• Myocardial perfusion imaging• Positron emission tomography• Magnetic resonance imaging

ECG changes

Stress echocardiography• echocardiography is performed both

before and after the exercise used to detect:

1. Wall motion abnormalities 2. Ejection fraction 3. Valvular heart disease

Nuclear stress test (Myocardial

perfusion imaging)• a radiotracer (Tc-99 sestamibi or thallium)

is injected• scans are acquired with a gamma camera

to capture images of the blood flow.• Usually done on two separate days:

1. After rest2. After injection of stress stimulating

drugs